Overview

This document provides a general overview of the Data Availability Layer (DAL) for the Tezos blockchain.

The present document extends the initial DAL design described here. In this document, we describe the P2P protocol of the DAL (also called DAL/P2P) that could be released for the first version of the DAL. For this first version, the DAL/P2P is based on gossipsub, an algorithm specified by the lib-p2p project and already used by many different blockchains such as Etheurem, Filecoin, Celestia, and more. Moreover, a security audit and evaluation report suggests it is resilient to various attack scenarios.

We also have implemented a simulation that suggests this algorithm is sufficient for supporting the DAL.

We also suggest various extensions of this design that could be released later. In particular, we discuss how this design could be enhanced so that we weaken the current assumption of the design that at least 32% of the stakeholders needs to be honest to guarantee data availibility.

This document is organised as follows:

• In the State of the art section, we explain the data availability, explain some folklore solutions to it and explain various designs related to the data availability problem used by other blockchains.

• In the DAL design section, we comprehensively describe the design we plan to implement for Tezos. At the time of writing, part of this design is already well integrated with Tezos.

• In the Towards a DAL V2 section, we explain how the design described in the previous section could be enhanced in the future, in particular to weaken the majority of honest attesters assumption.

• The Glossary section provides a glossary of the various specific terms related to data availability that will be found in this document.